The present invention relates generally to the field of substituted fullerenes. More particularly, it concerns substituted fullerenes and their use in compositions to ameliorate oxidative stress diseases or provide other antioxidant activities.
Reactive oxygen species (ROS), commonly referred to as “free radicals,” have been implicated in a variety of diseases. ROS are believed to promote, in at least certain cells, cell types, tissues, or tissue types, cell death (apoptosis), impaired cellular function, and modification or change in proportion of extracellular matrix components such as elastin or collagen, among other symptoms.
Buckminsterfullerenes, also known as fullerenes or, more colloquially, “buckyballs,” are cage-like molecules consisting essentially of sp2-hybridized carbons. Fullerenes were first reported by Kroto et al., Nature (1985) 318:162. Fullerenes are the third form of pure carbon, in addition to diamond and graphite. Typically, fullerenes are arranged in hexagons, pentagons, or both. Most known fullerenes have 12 pentagons and varying numbers of hexagons depending on the size of the molecule. Common fullerenes include C60 and C70, although fullerenes comprising up to about 400 carbon atoms are also known.
C60 has 30 carbon-carbon double bonds, and has been reported to readily react with oxygen radicals (Krusic et al., Science (1991) 254:1183–1185). Other fullerenes have comparable numbers of carbon-carbon double bonds and would be expected to be about as reactive with oxygen radicals. However, native fullerenes are generally only soluble in apolar organic solvents, such as toluene or benzene. To render fullerenes water-soluble, as well as to impart other properties to fullerene-based molecules, a number of fullerene substituents have been developed.
Methods of substituting fullerenes with various substituents are known in the art. Methods include 1,3-dipolar additions (Sijbesma et al., J. Am. Chem. Soc. (1993) 115:6510–6512; Suzuki, J. Am. Chem. Soc. (1992) 114:7301–7302; Suzuki et al., Science (1991) 254:1186–1188; Prato et al., J. Org. Chem. (1993) 58:5578–5580; Vasella et al., Angew. Chem. Int. Ed. Engl. (1992) 31:1388–1390; Prato et al., J. Am. Chem. Soc. (1993) 115:1148–1150; Maggini et al., Tetrahedron Lett. (1994) 35:2985–2988; Maggini et al., J. Am. Chem. Soc. (1993) 115:9798–9799; and Meier et al., J. Am. Chem. Soc. (1994) 116:7044–7048), Diels-Alder reactions (Iyoda et al., J. Chem. Soc. Chem. Commun. (1994) 1929–1930; Belik et al., Angew. Chem. Int. Ed. Engl. (1993) 32:78–80; Bidell et al., J. Chem. Soc. Chem. Commun. (1994) 1641–1642; and Meidine et al., J. Chem. Soc. Chem. Commun. (1993) 1342–1344), other cycloaddition processes (Saunders et al., Tetrahedron Lett. (1994) 35:3869–3872; Tadeshita et al., J. Chem. Soc. Perkin. Trans. (1994) 1433–1437; Beer et al., Angew. Chem. Int. Ed. Engl. (1994) 33:1087–1088; Kusukawa et al., Organometallics (1994) 13:4186–4188; Averdung et al., Chem. Ber. (1994) 127:787–789; Akasaka et al., J. Am. Chem. Soc. (1994) 116:2627–2628; Wu et al., Tetrahedron Lett. (1994) 35:919–922; and Wilson, J. Org. Chem. (1993) 58:6548–6549); cyclopropanation by addition/elimination (Hirsch et al., Agnew. Chem. Int. Ed. Engl. (1994) 33:437–438 and Bestmann et al., C. Tetra. Lett. (1994) 35:9017–9020); and addition of carbanions/alkyl lithiums/Grignard reagents (Nagashima et al., J. Org. Chem. (1994) 59:1246–1248; Fagan et al., J. Am. Chem. Soc. (1994) 114:9697–9699; Hirsch et al., Agnew. Chem. Int. Ed. Engl. (1992) 31:766–768; and Komatsu et al., J. Org. Chem. (1994) 59:6101–6102); among others. The synthesis of substituted fullerenes is reviewed by Murphy et al., U.S. Pat. No. 6,162,926.
Bingel, U.S. Pat. No. 5,739,376, and related published applications, is believed to be the first to report tris-malonate fullerene compounds, referred to below as C3 and D3. Dugan and coworkers at Washington University, St. Louis, have reported that C3 and D3 are useful for neuroprotection against amyotrophic lateral sclerosis (ALS, colloquially Lou Gehrig's disease) and related neurodegenerative diseases which are caused by oxidative stress injury (Choi et al., U.S. Pat. No. 6,265,443; Dugan et al., Parkinsonism Rel. Disorders 7:243–246 (2001); Dugan et al., Proc. Nat. Acad Sci. USA, 93:9434–9439 (1997); and Lotharius et al., J. Neurosci. 19:1284–1293 (1999)). C3 and (to a lesser extent) D3 have also been shown to provide either in vitro or in vivo benefits in protecting against other oxidative stress injuries (Fumelli et al., J. Invest. Dermatol. 115:835–841 (2000); Straface et al., FEBS Lett. 454:335–340 (1999); Monti et al., Biochem. Biophys. Res. Commun. 277:711–717 (2000) Lin et al., Neurosci. Res. 43:317–321 (2002); Huang et al., Eur. J. Biochem. 254:38–43 (1998); and Leonhardt, PCT Publ. Appln. WO 00/44357) and in inhibiting Gram-positive bacteria (Tsao et al., J. Antimicrob. Chemother. 49:641–649 (2002)).
Although C3 and D3 are capable of at least some scavenging of reactive oxygen species implicated in oxidative stress diseases, a need remains for fullerene derivatives which can ameliorate oxidative stress diseases, and especially for such fullerene derivatives which are superior to C3 or D3.